With the rapid development of computer, electronic and communication technology, various wireless communication services using a wireless network have been provided. The most basic wireless communication service is a wireless voice communication service for providing voice communication to mobile communication terminal users in wireless manner, which has a characteristic of providing the service to the users regardless of time and place. Further, the wireless communication service supplements a voice communication service by providing a text message service. Recently, a wireless Internet service has emerged, which provides an Internet communication service to mobile communication terminal users through a wireless network.
With the development of mobile communication technology as described above, a service provided by a CDMA mobile communication system is being developed to a multimedia communication service for the transmission of data such as circuit and packet data, including a conventional voice service.
Recently, with the development of information communication, an International Mobile Telecommunication (Hereinafter, referred to as IMT)-2000, e.g., a CDMA 2000 1X, 3X, EV-DO or a Wideband CDMA (WCDMA), has been commercialized, which is the 3rd mobile communication system and has been established as a standard by an International Telecommunication Union Recommendation (ITU-R). Further, a wireless Internet service has been provided at a transmission speed of 307.2 Kbps at maximum far faster than 14.4 Kbps or 56 Kbps, which is a data transmission speed supported by an Interim Standard (Hereinafter, referred to as IS)-95A network or an IS-95B network, by means of an IS-95C network evolved from the existing IS-95A network and IS-95B network. In particular, an IMT-2000 service is used, so that the quality of an existing voice and Wireless Application Protocol (WAP) service can be improved and various multimedia services, e.g., Audio On Demand (AOD), Video On Demand (VOD), etc., can be provided at higher speed.
However, because the existing mobile communication system has high base station installation cost, service charges for the wireless Internet are high. Further, because a mobile communication terminal has a small screen, available content is restricted. Therefore, there is a limitation in providing an ultra high-speed wireless Internet service. Furthermore, because Wireless Local Area Network (WLAN) technology shows radio wave interference, narrow service coverage, etc, there is a limitation in providing a public service. Accordingly, a High-speed Portable Internet (Hereinafter, referred to as HPi) system has emerged, which can guarantee portability and mobility and an ultra high-speed wireless Internet service at low cost.
In an HPi system, users access the Internet by means of various portable mobile communication terminals such as notebooks, PDAs and handheld PCs in stationary indoor and outdoor environments and mobile environments involving movement at various speeds, thereby receiving a service including various information and contents. Further, an HPi system provides mobility of 60 km/h, which is an Internet Protocol (IP)-based wireless data system having an upload/download asymmetric transmission characteristic in which a download transmission speed is 24.8 Mbps and an upload transmission speed is 5.2 Mbps.
An HPi system uses a 2.3 GHz frequency band, uses a Time Division Duplex (Hereinafter, referred to as TDD) as a duplex scheme, and uses an Orthogonal Frequency Division Multiple Access (Hereinafter, referred to as OFDMA)/a Time Division Multiple Access (Hereinafter, referred to as TDMA) as a multiple access scheme. Herein, the OFDMA/TDMA is a multiple access scheme similar to a TDMA which allocates all sub-carriers in an entire bandwidth to one user during a predetermined time period and then allocates all sub-carriers to another user during the next predetermined time period.
With the introduction of the new system as described above, an inter-working between an existing network and a new network is required. Because users require various services not restricted to a network type, an inter-working network for meeting the user's requirements has been visually constructed. For the construction of such an inter-working network, research into the 3G mobile communication and the WLAN has been actively pursued. However, these networks have been independently developed and have used different standards. Accordingly, for an inter-working between these networks, it is necessary to consider and update various items such as architectures, protocol structures, mobility, Quality of Service (QoS), authentication, security and accounting.
From the standpoint of a network, a 3G-WLAN inter-working scheme may be classified into a loosely-coupled inter-working scheme and a tightly-coupled inter-working scheme.
According to the loosely-coupled inter-working scheme, a 3G network and a WLAN exist separately and provide independent services, and a gateway for authentication and accounting is additionally provided in order to perform a roaming service requiring an inter-working, etc. Further, the mobility between the 3G network and the WLAN is based on a Mobile IP (MIP).
According to the tightly-coupled inter-working scheme, a WLAN Access Point (AP) connects to a 3G data core network and enables integrated user authentication/accounting and integrated network management to be performed, and it is possible to provide a continuous service, as compared with the MIP-based loosely-coupled inter-working scheme.
Meanwhile, in constructing an inter-working network of an existing network, such as a CDMA 2000 network, and a portable Internet network, because the CDMA 2000 network has already provided a commercial service with a sufficient infra structure, an inter-working scheme requiring the change of the CDMA 2000 network may not be a desirable scheme from the standpoint of a network provider. Accordingly, in constructing the inter-working network of the CDMA 2000 network and the portable Internet network, it is preferred to use a scheme capable of minimizing the change of the network as much as possible.
In this case, the inter-working scheme of the portable Internet network is performed in a manner similar to that of the 3G network and the WLAN. In the CDMA 2000 network, a message for reporting network information including an Access Network ID (Hereinafter, referred to as ANID) for reporting information for a current access network has been basically defined, and a transfer scheme of the message has also been standardized. However, in the portable Internet network, both an acquisition scheme of such an ANID message and a transfer scheme of the ANID message have not been defined. Accordingly, for handoff and roaming, it is necessary to additionally provide a scheme for acquiring the ANID of the portable Internet network and then transferring the acquired ANID.